Ribbon cable consists of multiple wire conductors running parallel to each other concealed within an insulating sheath. The conductor wires in ribbon cable can be either solid or stranded. Stranded wire consists of multiple strands of wire twisted together to form a heavier gage wire.
It is advantageous to keep conductor spacing consistent throughout the length of the cable to achieve maximum cable performance and to achieve quality in manufacturing operations. Industry demands require cable with conductor spacing as small as 0.025 inch. Previously invented instruments that measure conductor spacing do not have accuracies known to be capable of measuring conductors with 0.025 inch center to center spacing. Thus, there is a need in the cable manufacturing industry for a system and method that is able to accurately measure ribbon cables with conductor center to center spacing as small as 0.025 inch.
Direct visual or optical measurement of the conductor spacing is not possible due to the insulating sheath. Therefore, methods have been developed using X-ray technology to measure the center to center distance.
European Patent Application number 86309429.8 by Shuttleworth et al. discloses a method and apparatus for measuring center to center spacing of conductors in ribbon cable. The system involves passing a ribbon cable between a photon source and a detector in order to obtain the X-ray signal emerging from the cable. The signal is electronically processed and the resulting output is a waveform. The center to center distance of the conductors is represented as the distance between the troughs in the waveform. The location of the center of each conductor is determined by first establishing threshold positions where the waveform crosses a predetermined reference level. The trough positions can then be estimated by calculating the mean of adjacent threshold positions.
There is a need in the cable industry for a system and method for more accurately determining center to center conductor spacing in insulated flat cables. There is also a need for a system that is capable of determining center to center conductor spacing in insulated flat cables that use stranded wire conductors.